Brain volume changes after MR-guided focused ultrasound thalamotomy in patients with essential tremor and Parkinson’s disease

Abstract

Abstract Background Magnetic Resonance-guided Focused Ultrasound (MRgFUS) thalamotomy is a recently developed technique for treatment of severe tremor syndromes. Less is known about potential cortical and subcortical structural changes after ablation of the ventral intermediate nucleus and how these are potentially related to tremor relief.Methods Using an automated artificial-intelligence based approach, cortical and subcortical brain volume changes were investigated in 49 patients with essential tremor (ET) and 19 patients with tremor-dominant Parkinson’s disease (tdPD) before and six months after MRgFUS. Clinical outcome was assessed using the Clinical Rating Scale for Tremor. To evaluate differences in brain volumes, patients were further categorized into a high and low tremor improvement (TI) group.Results Brain volumes did not differ significantly between ET and tdPD patients at baseline. In both entities, significant volume reductions were found in the thalamus treated with thalamotomy along with volume increases in the occipital lobe contralateral to the MRgFUS lesion. Furthermore, significant differences between high and low TI groups were found in the contralateral occipital lobe in both entities, and in the contralateral caudate nucleus in tdPD patients. A significant volume reduction was found in tdPD patients with high TI in ipsilateral parietal lobe, ipsilateral putamen, and contralateral pallidum.Conclusion Our results indicate that TI achieved by MRgFUS thalamotomy affects a complex basal ganglia-thalamo-visuo-cortical network in patients with ET and tdPD. We identified a consistent spatial pattern of brain volume changes, particularly occipital lobe enlargement contralateral to the thalamotomy side, strongly suggesting possible restorative/reshaping effects after TI.